RFR: JDK-8170077 Properly parallelize javadoc generation

Mon Nov 21 09:25:32 UTC 2016

The current javadoc generation first creates the coredocs Javadoc, and 
after that all the remaining javadoc instances.

This dependency is not really needed, all that is required is that the 
remaining javadoc instances gets a proper pointer to a package-list file 
for coredocs. Fixing that will allow them to run in parallel with the 
coredoc generation.

In addition to this performance fix, I've also cleaned up the (now 
unnecessary) logic of storing the javadoc command line in 
.options/.packages files.

Bug: https://bugs.openjdk.java.net/browse/JDK-8170077
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8170077-parallelize-javadoc/webrev.01

/Magnus